The hectic schedule of football competitions implies that player
turnover is a hot topic in the professional game. This paper
compares strategies followed by big-5 league clubs according to
their last season's results and allows us to highlight best
practices in this area.

In order to effectively carry out this study, the teams of the
five major European championships are divided into four tiers
according to their sporting level. This is measured through the
CIES Football Observatory coefficient - a calculation that combines
the percentage of points won in European club competitions during
the last five seasons by the representatives of a national
association and the number of points per match obtained by teams in
their respective championships during the 2011/12 season.

The coefficient thus allows us to determine four club tiers, of
which the first one for the 2011/12 season is composed of the
following teams: Real Madrid, Manchester United, Manchester City,
Barcelona, Borussia Dortmund, Juventus, Bayern Munich, Tottenham
and Arsenal.

Results presented in this paper are part of the CIES Football
Observatory Annual Review 2012 that will be officially launched in
August. The specific section on player pitch performance is already
available by pre-ordering the full study. For more information see
www.football-observatory.com/publications
or write to football.observatory@cies.ch.

How to measure player turnover?

Player turnover may be measured in different ways. A first
indicator is the overall number of players fielded during the
season. As for the English Premier League, more and more
championships are introducing squad size limitations. The analysis
of the number of players used according to the sporting level of
clubs is thus very interesting also from a game governance
perspective.

A second indicator we can use to measure player turnover is the
cumulated percentage of minutes played from the most to the least
fielded footballer. This statistic complements to the previous one
insofar as it enables to compare the distribution of minutes among
first team squad members and to highlight to what extent coaches
rely on a core group of key players. The average percentage of
minutes played by the most fielded players can also be used for the
same purpose.

A third pertinent indicator refers to the average number of
changes in the starting 11 decided by club managers from one
championship match to the next one. While injuries are a
major factor in influencing coaches' decisions, it also allows us
to see any alterations that managers make on a game by game
basis.

A fourth indicator is the overall number of different line-ups
used by managers during the season. Again, this enables us to
understand to what extent managers rotate players on the pitchand
is ideally complemented by a fifth indicator that tracksthe number
of minutes played using these different line-ups.Players
fielded

None of last season's big-5 league champions fielded more than
25 players. Moreover, none signed more than three footballers
during the last winter transfer window. This shows that regardless
of the existence of squad size limitations, the best performing
clubs tended to be fairly parsimonious in the overall number of
players fielded. All title winners figure among the five clubs
having utilised the least players in their respective league. No
big-5 league club has used as few players as German Bundesliga and
Champions League runner-up Bayern Munich (21).

Figure 1: overall number of players used by big-5 league
champions (season 2011/12)

Tier 4 teams have on average fielded almost two more players
that Tier 1 clubs (28.3 compared to 26.4). This confirms that
having a large first-team squad does not naturally result in
success. Conversely, the over-use of players tends to exert a
negative impact on club results. From this perspective, the
over-activity on the transfer market can be seen a sign of future
difficulties even more than as the consequence of poor past
results.

Figure 2: overall number of players used during the
season, per big-5 league club tier (season 2011/12)

Percentage of minutes of the most fielded
players

The percentage of minutes played by the 11 most fielded
footballers out of the total minutes played by all squad members
was always greater among big-5 league champions than for second
ranked clubs. The average percentage of minutes played by the four
most used defensive and offensive players was also greater for
title winners than for the runners-up . The minimal value for a
title winner was 73.2%.

This finding confirms the importance of having a core group of
players on whom to count for all occurrences. It also allows to
highlight the negative impact that injuries can have on results.
While the effects of a long term injury on the squad as a whole are
mostly unpredictable, it is noticeable that injuries have
negative consequences for those teams that have arguably
'like for like' substitutes. This holds particularly true for
defensive positions.

For all 2011/12 champions except Borussia Dortmund, the average
percentage of minutes played by the four most fielded defensive
players (not including goalkeepers) was greater than for the four
most fielded offensive footballers.

Figure 3: average percentage of minutes played by the
four most used defensive and offensive big-5 league champions'
players (season 2011/12)

Generally speaking, the best performing clubs rely more than any
other team on a core group of players to make up their line-ups.
The five most fielded players in Tier 1 teams have played 40% of
the total minutes played by all squad members. This figure goes
progressively down in parallel with the sporting level of the
clubs. The fifteen most fielded Tier 1 club footballers played
almost 90% of total minutes (compared to about 83% for Tier 4
teams).

Figure 4: cumulated percentage of minutes played by the
5, 10 and 15 most fielded footballers, per club tier (season
2011/12)

Changes per match

During last season, all title winners also changed fewer players
in the starting eleven than runner-up teams (the only exception is
Manchester City , who used exactly the same number of players as
Manchester United). The wealthiest clubs among champions changed
more players on average than the poorest ones. While Real Madrid
changed on average almost three players from one match to the next,
this figure is one third lower for German champions Borussia
Dortmund.

Figure 5: average number of changes in the starting 11
from a championship match to the successive one for big-5 league
champions (season 2011/12)

However, the analysis by club tier shows that the best
performing teams tend to change more players in the initial line-up
than those performing least well. This is probably due to their
participation in European cup competitions, as well as the presence
in the squad of more players with a similar sporting level. This
strategy is also probably related to the attempt of preventing
injuries that can prove to be extremely detrimental from a longer
term perspective. However, it must be noted that the gaps recorded
are not statistically significant.

Figure 6: average number of changes in the starting 11
from a championship match to the successive one, per club tier
(season 2011/12)

Different line-ups fielded

Four champions out of five are in the last five positions of
their league ranking concerning the number of different line
ups fielded over the course of the season. The only exception is
Manchester City. The team coached by Roberto Mancini fielded 138
different line-ups, the highest figure in the English Premier
League (+20 compared to Manchester United). In all other cases,
league winners used fewer formations than runner-up teams.

Figure 7: overall number of formations fielded over the
course of the season by big-5 league champions (season
2011/12)

By club tier, while the differences are not very marked, the
best performing clubs also used fewer different line-ups during the
2011/12 season than lower tier teams. This tends to confirm that
too many changes to a starting line-up are detrimental to success
and that it is worth trusting players even in difficult situations.
The figures appear to indicate that clubs run by managers who are
more resistant to panic are in a better position to maintain good
performance levels over the long term.

Figure 8: overall number of formations fielded over the
course of the season, per club tier (season 2011/12)

This result is reinforced by the data on the percentage of
minutes played by the most used formations. The five most fielded
Tier 1 club line-ups have on average played 22.4% of total minutes,
a greater figure than for any other team tier. The positive gap is
also to be found for the 10th (34.3%), 25th
(61.3%) and 50th (82.5%) most used line ups.

Figure 9: cumulated percentage of minutes played by the
5, 10, 25 and 50 most fielded player combinations, per club tier
(season 2011/12)

Best practices

While they use fewest players over the course of a season and
rely more on core group of key players, the best performing clubs
tend to change more players in the starting 11 from one match to
the next. However, during last season, winning teams also averagely
changed fewer footballers than runner-up clubs.

These findings suggest that the best solution is to have seven
to eight stable players in the line-up, plus six to eight
interchangeable players. In this way, clubs are able to maintain
stability and cohesion, while preserving the physical capital of
footballers playing in the positions where freshness is
particularly important (mostly offensively).

Irrespective of club wealth, our analysis suggests that it is
recommended that clubs concentrate financial efforts on a core
group of players instead of increasing the number of first team
members at all costs. In other words, quality is worth more than
quantity. While the requirement to have competitive substitutes
plays a part in achieving a competitive advantage held
by the best performing clubs -above all when it comes to replacing
long-term injured players - evidence shows that the real difference
is made by a relatively low number of players (around 16 per
season).

This is also illustrated by the fact that all 2011/12 champions
have at least seven players who are present in each of the three
most used line-ups. This figure is up to nine for Juventus,
Borussia Dortmund and Manchester City. The latter club is the only
title winner where the three most fielded line-ups do not include
the same defenders. From a success perspective, this clearly
confirms the importance of reducing player turnover in defence as
much as possible.

Other findings that are found in the 2012 CIES Football
Observatory Annual Review show that clubs run by patient managers
have a key competitive advantage compared to teams run by impulsive
ones. Indeed, cohesion and routines are crucial for success in
football. Statistical evidence shows that it is worth trusting
players even in difficult situations. Of course, this advice is
easier to follow when club results are satisfactory. However, in
all cases, an ability to manage the squad using a mid- to
long-term perspective, follow a coherent strategic line and to
resist to media and popular pressure are key success factors.

The main reason is probably that this will favour the creation
of a positive context where players more easily understand the
specific role that they are called on to play. This will enhance
their motivation to fully adhere to the sporting project of their
employer club which, in turn, puts them in the best condition to
continuously perform at their highest level possible. Many examples
show that top level performances are by far not only related to the
players' intrinsic talent, but also to the general environment of a
team.